1. Field of the Invention
The present invention relates to a binder, based upon an aqueous dispersion of polyvinylbutyral, for paint and varnishes.
2. Description of the Prior Art
Polyvinylacetals have valuable properties when used as coatings; however, it has hitherto been necessary to employ same in solution in organic solvents.
Various processes are known to the art which make it possible to obtain aqueous dispersions of polyvinylacetals. However, these dispersions exhibited a certain number of disadvantages, such as an inadequate solids content on the order of 15% and the presence of excessive amounts of hydrosoluble product as the emulsifier or protective colloid. These disadvantages prevented or very severely limited the use of these dispersions as varnishes or paints, especially those used as a primary coating or anti-corrosion coating on metal.